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Low Voltage Circuit Breaker Frequently-Asked Questions

Click on question marks below to get answers to these frequently-asked questions.

What are other names for low voltage circuit breakers?

Low voltage circuit breakers are sometimes referred to as just air circuit breakers, power air circuit breakers, power circuit breakers, power breakers, draw out air circuit breakers, or air breakers. A company that repairs, retrofits, maintains, tests, or sells circuit breakers would typically refer to them as low voltage circuit breakers. But an electrician in a manufacturing plant would just call them air breakers.

I know what a molded case circuit breaker is, but is an insulated case circuit breaker the same as a low voltage circuit breaker?

No, an insulated case circuit breaker is built totally different from a low voltage circuit breaker. An insulated case circuit breaker is more like a large molded case circuit breaker in that it is totally enclosed inside an “insulated case.” Where as an air circuit breaker is typically constructed within a metal frame.

Why would I use a big low voltage circuit breaker instead of a molded case circuit breaker or an insulated case circuit breaker?

Low voltage circuit breakers are physically durable breakers designed to handle heavy electrical loads reliably for a long time. They are typically drawout circuit breakers. A drawout air circuit breaker can be removed from an energized switchboard and be replaced or reinstalled without shutting off power. It is designed for facilities that have large power requirements and can not conveniently shutdown for long to maintain or repair a breaker. Air circuit breakers may have many auxiliary devices and controls such as a shunt trip, undervoltage trip, interlocks, and auxiliary contacts. They can be electrically operated for manual or automatic, remote or local opening and closing. They are very durable and can be built to handle large fault currents. They can even be fused for extremely high fault currents. And, if they are damaged, typically the damaged part can be replaced or repaired. Older breakers can easily be repaired, reconditioned, remanufactured, or retrofitted.

I see information about retrofitting air circuit breakers. What does that mean?

Many older low voltage circuit breakers are in good mechanical condition, but the overcurrent devices used on them when they were built may be obsolete, even unreliable. Some breakers have old oil dashpots as overcurrent devices; some use first generation electronic overcurrent devices that simply are obsolete and unreliable. These are replaced with state-of-the-art electronic overcurrent devices or programmers that provide much more sophisticated protection.

Who are some of the old and current manufacturers of air circuit breakers? Would I recognize them?

Certainly. They are Westinghouse, GE or General Electric, Allis Chalmers, Siemens Allis, Siemens, Square D, Cutler Hammer, ABB, BBC, ITE, old Roller Smith, and Federal Pacific. All manufacturers at one time or another of low voltage circuit breakers.

Quick links to other reconditioned, obsolete and used circuit breaker inventory:

Used, Reconditioned, Surplus, Obsolete Circuit Breakers

We carry all the top named manufacturers from ABB also known as Asea Brown Boveri to AIRPAX made by Sensata Technologies; Allen Bradley designed branch breakers; American and Bryant made; Everyone’s favorite breaker named Bulldog; We also handle Challenger, Crouse Hinds and Fuji; MIDWEST offers Eaton Cutler Hammer industrial made; Among our favorites are any breakers manufactured by GE General Electric; The no longer manufactured old Federal Pacific Electric; We are proud to handle the very popular Square D; We sell all catalog numbers of the universally found Westinghouse; Fill the growing requests for Merlin Gerin; We also provide Gould; Heinemann; ITE; ITE Siemens; MIDWEST also tests and sells Siemens; We handle Sylvania; Wadsworth; Challenger; Murray; We carry the less known Milbank; Moeller; National; In North America we feature Mitsubishi; Uncommon breakers provided are Sace; Telmand; Thomas and Betts; Trumbell; And many will recognize the name Zinsco.

by Square D and Eaton Cutler Hammer; MIDWEST also offers GE General Electric and Westinghouse; We handle the older Allis Chalmers and ITE and the old and newer Siemens; Look to us for ABB; And we have the really classic Roller Smith and not so old Federal Pacific.

MEDIUM AND HIGH VOLTAGE AIR AND VACUUM CIRCUIT BREAKERS MANUFACTURERS

Reconditioned, used, old, refurbished, obsolete and new

Medium and high voltage circuit breakers by GE General Electric, ABB, Siemens, or Eaton are available from MIDWEST. We also can fill the need for older Allis Chalmers, Federal Pacific or Westinghouse air or vacuum circuit breakers. Finally, see MIDWEST if you require Cutler Hammer, Square D, Toshiba, or McGraw Edison.

OIL CIRCUIT BREAKER MANUFACTURERS

Used, Reconditioned, Surplus, and Obsolete Oil Circuit Breakers

GE General Electric; Westinghouse are still available for your special needs.